A school maintenance worker smelled gas and warned people to get out of the building 1 minute before the deadly explosion at Minnehaha Academy on Aug. 2.
That's according to a preliminary report released Monday by the National Transportation Safety Board (NTSB), which is investigating the deadly explosion.
The report says the maintenance worked "heard and smelled" the natural gas and went to the source of the gas (in the basement of Minnehaha Academy's Upper School).
When leaving the basement, the worker – who wasn't identified in the report – used his hand-held radio to warn people to get out of the building right away.
As he was making the announcement, "he ran up the stairs and searched" for people inside, the report says.
The report says the explosion happened while two workers were installing new piping to relocate gas meters from the basement to the outside of the building.
"While workers were removing the existing piping, a full-flow natural gas line at pressure was opened. The workers were unable to mitigate the release of the gas, so they evacuated the area," the report says.
The NTSB's preliminary report doesn't make any conclusions about what happened, MPR News says, noting the agency will amend the report as its investigation continues.